The present invention relates in general to methods of sensing forces utilizing transducers and in particular to a method of measuring strain forces in an underdrive press.
The ability to measure force or load is vital part of many industrial processees. Recognizing that a structure undergoes dimensional changes when subjected to a load, a measure of the dimensional change in a structure can accurately indicate the amount of force applied thereto. Such measurement is usually made through the use of a wire, foil or semi-conductor element intimately bonded to the structure. By measuring the change in the electrical resistance of the element, which resistance is a function of the change in cross-section of the element due to alterations in the dimensions of a structure, it is possible to accurately measure the load applied to the structure.
In the case of metal stamping processees, the dangers associated with the improper adjustment of the press and associated dies include broken presses, smashed tooling, and high rejection rates for the stamped products. Many of these losses could be prevented if the human operator and/or a control circuit had access to an accurate indication of the loads being imposed upon the dies. In an underdrive press, where one or more upper slides are connected to a drive system with connecting rods, many prior art attempts have been made to measure the forces imposed upon the dies. Strain sensing transducers have been located on the dies, on the shoes, on the slides, and on the inside of the press bed to measure compressive forces, and on the connecting rods and on the pull rods to measure tension forces. However, these prior art methods of measuring the forces imposed upon the dies have provided less than satisfactory results.